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2006 chevy trailblazer_lt_ext
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Discussion Starter #1
06 trailblazer v6 4.2 ext lt

Parts replaced:
Oil pump/ timing chain cover assembly
Crank shaft
Crank shaft bearings
Piston rod bearings
Rear main seal
Oil filter bypass valve
Crank bolts
Water pump

After removing the oil pan to take off the oil pick up tube, we noticed that the number 2 cylinder rod had play in it on the crank shaft. We removed the rod cap and found the bearing worn thin and the crank shaft scored where it made contact with the bearing. A new crank shaft with crank and rod bearings as well as a new rear main seal were installed. All bearing clearances were checked with plasti-gauge to meet specifications and all bolts torqued to gm specs. New Oil pump and pick up tube were replaced on engine with new gaskets on pick up tube and pump with liquid gasket used on timing chain cover. Replaced water pump. Oil pan placed back on with liquid gasket. Allowed 24hrs for liquid gasket to cure before adding oil. Reattached flexplate, transmission, torque converter, exhaust, rack and pinion, steering shaft, drive shaft, cross braces, transmission cooler lines, hoses, and electrical connectors. Changed oil filter and refilled fluids. Added 5 quarts 5w-20 synthetic and 2 quarts 5w-30 synthetic. Started engine. In dash gauge showed normal oil pressure at first then dropped to no pressure at idle. Oil pressure would rise when pressing throttle but fall back to 0. Attached a manual oil pressure test gauge to check live pressure. Engine was still showing low pressure idling after warning up. Drained oil and added 7 quarts 10w-40 with bottle of oil treatment. Checked pressure with manual gauge with same results. Drained oil and removed oil pan to check pick up tube gasket. Found no problems with gasket. Replaced oil filter bypass valve. Returned oil pan and oil. Checked manual pressure, reading over 40psi on start then falling to around 2psi at idle after warning up. Revving engine raises psi to around 40 but falls back at idle.

Any ideas on what could be causing oil pressure to continue dropping and staying low to none?

Thank you
 

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2002 chevy trailblazer_ltz
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34 Posts
Oil passages blocking flow.

Sludge is your enemy. Who had it before and their oil change habits?

If they (or you) waited for 7000 miles before chamging then you have your answer.

Manual gauge? I assume you mean a mechanical gauge?

If you're talking an aftermarket electric gauge and you're using the oem sending unit... Then the sending unit is bad.

Good luck
 

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2006 chevy trailblazer_lt_ext
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22 Posts
Discussion Starter #5
No. We ended up rebuilding the bottom half of the engine. Completely. Drive it same damn thing. Us and 3 certified mechanics couldn't figure it out. So we just bought a whole another engine and replaced the dang thing. Now no more problems. I wish I could have figured it out but no way.
 

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2004 chevy trailblazer_ls
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333 Posts
Since you have a new running engine, I would have taken the old one apart to find out why. Curiosity would have killed me.
 

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2006 chevy trailblazer_lt_ext
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22 Posts
Discussion Starter #8
Mileage on failed engine was 155k
Couldn't tear it apart had to give it to salvage yard where I got new one with 175k. So far new one is great! More mileage but for less than 800 for full engine couldn't beat the price.
 

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  1. Mileage on failed engine was 155k
    Couldn't tear it apart had to give it to salvage yard where I got new one with 175k. So far new one is great! More mileage but for less than 800 for full engine couldn't beat the price.
    I had the same exact problem... It ended up being the oil pressure switch
 

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2004 chevy trailblazer_ls
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333 Posts
I've seen that happen (not on an Atlas), where the oil pickup was jammed against the pan, instead of an inch off the bottom.
 

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2006 chevy trailblazer_lt_ext
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Discussion Starter #12
Yeah we're checked even replaced the pickup tube. We replaced everything on the bottom half of engine. Still had no oil pressure.
 

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2008 gmc envoy_sle
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631 Posts
I can only assume there were blocked oil passages from sludge buildup, not much else makes sense.

hows the new one? still running good i hope.
 

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2006 chevy trailblazer_lt_ext
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Discussion Starter #14
Yeah that is all I can think of. Sludge build up somewhere we didn't see.
New one is running great!! Not bad for $900. Gotta keep my baby running since she's my only vehicle.
Now i just have to replace the rear heater box and actuators for rear ac. Ugh
 

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2004 chevy trailblazer_ls
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333 Posts
Back in the 90's, I worked at a dealership. Car came in that needed a crankshaft, and I put a new one in that parts had ordered, GM label on the box. Got it in-no oil pressure. Well, WTF.
Pulled it out, found out one journal on the main had some of the material from the grinding process stuck in the oil passage.
I was working piece work at the time, lost about a days pay.
 

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2006 chevy trailblazer_lt_ext
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Discussion Starter #17
Thanks y'all.
Yeah husband thinks it's either sludge build up or metal shavings somewhere we didn't look. But all good now with better running engine.
 
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